• • Phosphorus and tungsten co-modified ZSM-5 achieved the highest ethylene yield, with L acid amount of 18.3 μmol/g, strong Brønsted acid amount of 31.3 μmol/g, and L_T/B_T ratio of 0.37, demonstrating an optimal balance for mild dehydrogenation and cracking.
• • An excessively high L/B acid ratio (e.g., >0.37) promotes hydrogen and coke formation, leading to pore blockage and reduced conversion, thereby lowering ethylene and propylene yields; this underscores the need for precise acid-site engineering.
• • Reactant conversion follows the order n-heptane > 3-methylhexane > methylcyclohexane, correlating with molecular size and diffusional constraints in ZSM-5 micropores; efficient conversion of branched and cyclic C7 hydrocarbons requires high specific surface area and micropore surface area.
• • Modification with phosphorus and transition metals (except Cu and La) increased total Brønsted acid amount, while L acid sites were predominantly weak; this tunability allows optimization of dehydrogenation versus cracking pathways for enhanced light olefin production.